There have long been efforts to construct buildings and tents that span a floor area without the need for intrusive interior supports. The typical approach is to assemble a framework of rigid linear materials, which is then covered with a surfacing material, or skin.
Stresses must be carried by a combination of tension and compression members, organized into a system that carries the distributed loads of the skin, and focuses them onto several support points on the ground. The total of all compression forces equals the total of all tensile forces. When seen together, the pathways of these forces form triangular patterns within the whole structure, and these patterns are best managed by designing triangles directly into the framework.
From the simplest to more complex space-enclosing shapes:
(1) The traditional pup-tent, (a prism-shape, or, alternatively, a pyramid shape), had to be anchored to the ground, in part to make more usable interior space by pulling the sagging skin outward. This puts additional tension on the skin, and compression on the poles. It also takes up space on the exterior, making it difficult to walk around the tent without tripping on these tension lines. Other prism shapes, such as the “A-frame” buildings, also have problems, one of the biggest being their large surface areas, through which heat is lost.(2) Another traditional solution has been to use a cubical configuration, in which the walls are vertical, and are made rigid by the application of sheathing materials or diagonals inserted into the framing. The roof is typically constructed by means of trussing, resulting in either a peaked or a flat roof. A big drawback is that this type of building requires more lumber per square foot of usable space than either a geodesic dome, or a “hypershelter”. A lot of material is used in the trusses, and the over-all building is thus top-heavy. A volume of the covered space is unusable, being inside the jungle of triangles in the attic. The instant invention contains a greater usable volume for a given surface area than any cubical structure, and is therefore more economical both in the expenditure of materials, and in the amount of labor required.(3) A solution recently employed has been to use a dome shape with the outward forces being supplied by very long tent-poles, held under constant stress by being bent. This is very workable on small scales, and yields good strength-to-weight ratios as well as high volume-to-surface-area ratios because of the near-hemispherical shape. However, such stressed arches are not effective when rigidity is desired, and it is difficult to apply to larger structures for two reasons: (A): Assembling long, continuous, stressed framing members becomes more unwieldy as size increases, and (B): Strength-to-weight ratios decrease as overall size increases, because weight goes up on a function of the cube of the increase, whereas strength only increases on a squaring function. This makes it difficult to find the appropriate material of sufficient resiliency to support its own weight when used as a stressed arch.(4) The use of panel constructions which can be assembled into building structures of various sizes, shapes, and types. Systems for attaching the panels to each other; and building structures of panel-type construction, are well known in the art. For example, see U.S. Pat. No. 3,945,160 to Grosser.(5) Also known in the art is the assembling of panel constructions into geodesic dome structures. For example, see U.S. Pat. No. 4,160,345 to Nalick. The connectors for forming the structures by joining panel construction together is also well known in the art. For example see U.S. Pat. No. 6,173,547 to Lipson. When constructing a geodesic dome type structure such as in U.S. Pat. No. 2,682,235 to Fuller, or U.S. Pat. No. 6,295,785 to Herrman, a bottom edge is created that is typically raised over a substantially cylindrical portion into which doors and windows are fitted. As with these references and with U.S. Pat. No. 5,305,564 to Fahey, cells are typically arranged in circular rows. Each cell has edges, and as with triangles, they require special connectors and edge materials, which increase the cost of construction.The geodesic dome, (U.S. Pat. No. 2,682,235 to Fuller,) has many advantages which are achieved by means of straight-member, all-triangle framing where all stress problems are dealt with directly, the forces being sent predictably along straight struts. The weight is distributed downward and outward along these, and rests on the base at many points. The curved shape, and the orientation of the struts means that most struts act in compression to carry weight loads, though any strut can also come under tension, depending on specific forces acting on the whole structure.On a large scale, the dome is assembled from a multiplicity of smaller pieces, and is usually covered with some rigid surfacing material, which acts, at shared edges, to reinforce the struts. While not containing quite the volume per unit surface area of the geodesic dome, the instant invention, hypershelter has the above advantages of the geodesic dome, but avoids the following disadvantages:Problems arising in construction of a geodesic dome:1) The triangles, though mass-producible in repeating patterns in a geodesic dome, create challenges in cutting covering materials, because these are commonly produced in rectangular forms, and require cutting to specifications which inevitably entail waste of unusable scraps.2) The erection of the framework of a geodesic dome usually involves assembling the struts into successive courses of triangles, which, on large scales, requires the use of a crane and/or scaffolding. These initial courses are very unstable until the succeeding courses are assembled on them.3) There are a large number of edges between triangles in a geodesic dome, and these constitute a very great length, simply because the triangle is the shape with the most perimeter to surface area. Although the planes join at obtuse angles so the ridges are less sharp, these edge lengths constitute a serious problem for the geodesic dome. The instant invention requires a minimum of such ridges, or edges. An N-way hypershelter has only N ridges.4) Associated with the above is the difficulty of creating openings such as windows and doors, which must either be restricted within given triangles, or require the radical shape and re-engineering required in the creation of dormers or other protrusions. Openings such as skylights made in roof panels also engender the care and expense required in waterproofing.5) Another drawback of the geodesic dome structures is that highly sophisticated crews and specialized connecting hardware must be employed for construction.The hypershelter configuration has the capability of spanning large areas without the requirement that there be any internal supports. In this regard, it resembles a dome structure, such as the geodesic, which can be varied to span larger areas per height by taking a shallower slice of the sphere. In the hypershelter, a similar variation can be achieved by using shorter leg members, and varying the height of the apex. But, the hypershelter spans these large areas while allowing large openings at the periphery for the ingress and egress of goods and people. These openings are triangular, making them rigid by design, and can be varied down to lower profiles while remaining vertical. Additional vertical supports can then be added without interfering with the over-all utility of the structure. The shape of the over-all structure sweeps out to these openings along the smooth curvature of the hyperbolic paraboloid faces, so that there is no need for sudden protrusions and sharp-edged valleys, as in the typical dormer constructions.The main spanning members in the roof are at the ridges, so each is at the edge of two convergent planes. The planes are leaning in compression against each other. Thus, their own weight is being supported by the structural members of these planes, and distributed downward across their faces. The great spanning capacity is thus accomplished without the need for the multiplicity of faces, edges, struts, or connectors occurring in the geodesic dome. Related to these benefits is that the hypershelter can be covered in large, continuous areas, rather than piecemeal.
Other structures, most notably roofs, have been made using hyperbolic paraboloids for the beauty and great strength afforded by such. See H. H. Charles, U.S. Pat. No. 3,186,128. Also, Eugene Pryor, U.S. Pat. No. 3,757,478 and Paul T Hodess, U.S. Pat. No. 3,846,953, beams hinged for erection of hyperbolic paraboloid roofs; and Harry L Guzelimian, U.S. Pat. No. 3,280,518, Curved roof support system; and. Daniel F. Tully U.S. Pat. No. 4,137,679, Inverted, doubly-curved umbrella hyperbolic paraboloid shells with structurally integrated upper Diaphragm; and Ray A Woods U.S. Pat. No. 5,020,287 Structural Building Components; and Solomon Kirschen U.S. Pat. No. 4,320,603 Roof construction; and Arthur T Brown, U.S. Pat. No. 3,200,026 Method of producing a Shell Roof structure; and Peter E. Ellen, U.S. Pat. No. 5,069,008 Building panel.
But, in those constructions, the builders have resorted to the use of expensive pre-formed panels to achieve the compound curvature required in a hyperbolic paraboloid shape, or other elaborate preforms, or have designed complex connectors. The instant invention achieves the hyperbolic paraboloid shape by the use of commonly available framing materials, applied successively to an under-framing, and covered with strips of roofing material (such as sheet metal, plywood, thatching, etc) successively bent into place while being applied. In the preferred hypershelter, the completed structure efficiently encloses volumes, as well as providing roofing for covering areas, because the lower portions of the hyperbolic paraboloid faces act partly as walls. Problems in the erection of the frameworks are also overcome in the instant invention by the pre-assembly on the ground, and wholesale, umbrella-like deployment of the framework as described herein.
It would therefore be beneficial to have a structural configuration and method for erecting same that encloses a large volume per unit surface area, and minimizes the need for edge connectors, specialized strut connectors, or custom dormers, and provides for openings that can be used as windows or doors, and is capable of being constructed by average unskilled or semi-skilled crews. This is possible with the instant invention.